This story appears in the January 2011 issue of National Geographic magazine. If they ever build a Wal-Mart at Machu Picchu, I will think of Collinsville Road. I'm standing at the center of what ...

The ancient North American city of Cahokia had as its focal point a feature now known as Monks Mound, a giant earthwork surrounded on its north, south, east and west by large rectangular open areas.